Integrated Scheduling of Unicast and Multicast Traffic in an Input-Queued Switch

We consider the problem of scheduling packets in an input-queued switch when both unicast and multicast traffic is present. In contrast to current approaches which mostly isolate unicast from multicast, we propose an integrated schedule that packs unicast cells into idle slots left by the multicast schedule. While the optimal integrated schedule can be shown to be NP-hard to obtain, we propose both off-line and on-line algorithms with strong theoretical guarantees to perform integration efficiently. Simulations suggest substantial improvement in switch throughput using the integrated schedule. To further reinforce the importance of performing integration, we study the multicast scheduling problem with and without fanout splitting. Again, we prove hardness of the problem and several of its variants, and propose competitive algorithms. The hardness of multicast scheduling hence emphasizes the importance of integrated scheduling for switch performance.